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From: michaelv@MindBender.HeadCandy.com (Michael L. VanLoon)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: SCSI card
Date: 09 Sep 1996 16:05:26 GMT
Organization: HeadCandy Associates... Sweets for the lobes.
Lines: 75
Message-ID: <MICHAELV.96Sep9090526@MindBender.HeadCandy.com>
References: <Pine.SOL.3.93.960903215141.13825B-100000@bmec.hscbklyn.edu>
NNTP-Posting-Host: mindbender.serv.net
In-reply-to: David Zakai's message of Tue, 3 Sep 1996 22:05:10 -0400
In article <Pine.SOL.3.93.960903215141.13825B-100000@bmec.hscbklyn.edu> David Zakai <zakaid99@hscbklyn.edu> writes:
I intend to get a Pentium 166 MHz PCI computer with an EIDE
hard disk, because the card/drive combination is much cheaper,
even if I equip the computer with a separate SCSI card to run
other peripherals, like tape backup, CDROM, etc.
You should check again. There is very little difference in price
between a SCSI and EIDE version of the same drive, in general. If the
place you're buying it from is telling you different, you should check
some other sources. You will get a big boost in "responsiveness" by
going SCSI.
1. Are there still significant incompatibilities when using
a PCI-based card (like Adaptec AHA-2940 or AHA-2920) instead
of ISA-based cards like Adaptec AVA-1522B ?
What "incompatibilities"? You can use an Adaptec 2940-2940UW,
BusLogic BT9[45][68], and/or NCR (sorry, Symbios) 53c8xx-based SCSI
card.
You should also note that the NCR/Symbios cards are very inexpensive
compared to the others (under $100).
A 1522 would be about your absolute worst choice. Forget about any of
the claimed benefits of SCSI if you go that direction. Even a 1542 is
going to be *significantly* slower than a PCI adapter.
2. Is the performance boost significant for PCI versus ISA cards
(when PCI are double the cost) ?
Yes.
3. Is there a significant performance boost when using
bus mastering versus PIO (programmed IO) Adaptec cards?
Well, it depends on what you're doing. You will get a significant
boost in concurrent processing, which means it might not benchmark
faster, but will generally "feel" more responsive. If you have
really heavy-disk usage, it will definitely be faster. But your
circumstances dictate just how "significant" this boost is.
(I don't think that I shall gain much advantage for tape
backup, but the Iomega JAZ drive has a Fast SCSI2 interface.)
So get a SCSI hard drive.
4. If the computer's primary drive is an EIDE disk, can one
install a SCSI card with an onboard BIOS and boot from
an external bootable device like an Iomega JAZ drive ?
Yes. You turn the EIDE hard drive off in the BIOS (so the BIOS
doesn't think it's there). It will boot the first SCSI drive.
FreeBSD will then detect all your EIDE devices while it's booting (it
actively probes them, rather than just believing what the BIOS tells
it).
The primary disk will probably have Win95.
This is the only place really to use EIDE, since I'm pretty sure that
Win95 doesn't do bus-mastering, so doesn't gain much of an advantage
with SCSI (speed-wise, anyway; there are all those other advantages,
like seven devices per bus, none of this master/slave crap, everything
"just works" without all the screwing around and manufacturer
incompatibilities that EIDE is famous for, etc.).
--
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Michael L. VanLoon michaelv@MindBender.serv.net
--< Free your mind and your machine -- NetBSD free un*x >--
NetBSD working ports: 386+PC, Mac 68k, Amiga, Atari 68k, HP300, Sun3,
Sun4/4c/4m, DEC MIPS, DEC Alpha, PC532, VAX, MVME68k, arm32...
NetBSD ports in progress: PICA, others...
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